SWFC’s Anna Heaton reports on a fascinating workshop at ORFC 2021 on controlling internal parasites without anthelmintics
Resistance to anthelmintics is an increasing problem in the UK, with some farms reporting multiple resistance to more than one class of wormer. And if you’re an organic farmer, you’ll no doubt be aware of the growing momentum within the sector to identify ways to reduce reliance on so-called “contentious” inputs—including wormers.
The ‘Natural Worm Control Without Anthelmintics’ workshop at the recent Oxford Real Farming Conference 2021 included a summary of the research being done as part of the EU-funded Replacement of Contentious Inputs in Organic Farming Systems (RELACS) project, which is reviewing a range of products used in organic farming systems, such as livestock wormers, antibiotics, fertilisers, copper and vitamins. The ORFC workshop focused mainly on the potential for controlling worms using bioactive forages and nematophagous fungi.
Anthemlintic use on European organic farms
The first part of the workshop presentation included a review of the frequency of use of anthelmintics among European organic farmers, presented by Dr. Caroline Chylinski from SRUC. The research included a questionnaire for organic inspectors in Europe, which gained 139 responses from 16 countries representing over 17,000 organic farms. There was a wide variation from country to country, but the UK came out with 70% of organic farmers including wormers in their health plans as products used on-farm. This compared with only 25% of Danish organic farmers but 80% of Romanian organic farmers.
The initial survey was followed up with another direct survey to collect further information directly from individual farmers. In the UK, 343 organic farmers responded with a total of over 160,000 animals (mostly sheep and cattle) between them. Some 61% of those farmers said that they used anthelmintics, with 64% treating stock once or twice a year. Of those treatments, 65% were for 50% to 100% of their livestock: more than might have been expected for organic farms — and certainly offering room for improvement. To bring home the rationale behind this project, 18% of those farmers also reported anthelmintic resistance, mostly to benzimadazoles.
Alternative worm control
Next, Dr. Spiridoula Athanasiadou from SRUC talked about the problems faced by farmers and the approach taken by this project. Worm infections have a serious impact on livestock performance and lead to impaired food digestion, protein leakage and gut damage, leaving fewer nutrients available for the animal to grow and thrive. Although worming can reduce the problem, research shows that animals that are infected with worms and then treated with anthelmintics still have lower growth rates than those that are not challenged with worms at all.
Spiridoula explained that this project has a dual approach to reducing the worm challenge altogether, researching the impact of bioactive forages such as heather, which target the parasitic stages of worm development (inside the gut of the animal), and biocontrol agents such as nematophagous fungi, which target the free-living stages of the larvae (when they are outside the animal and developing on the pasture).
Heather: A bioactive forage
While previous studies have analysed the effectiveness of forages containing condensed tannins to reduce worm infection (plants like chicory and birdsfoot trefoil are often cited), this new study focused instead on heather, as it is abundant in Europe and in upland situations where some of the other anti-worm forages cannot be grown. Interestingly, the research showed that although all the heather tested was effective against parasites, there was variation across Europe and the heather in the UK and Spain were the most effective. In vitro studies also showed that heather affected abomasal worms more than intestinal worms, although both types were reduced.
Fungi for worm control
The second approach covered by the workshop was less familiar: using the fungi Duddingtonia flagrans to control worms in pasture. This nematophagous fungi kill free-living larvae stages on the pasture and can reduce contamination by 70% – a quite incredible figure.
A slide from the presentation showing nematodirus worm entrapped by fungi
The nematophagous fungi are already commercially available in some countries, such as Australia. The fungi are fed to the animal where it passes through the digestive tract leaving fungal spores in the dung. The spores then germinate and attack the parasite larvae. Importantly, there is no negative impact of the fungi on other soil nematodes and no issues for the animal.
UK, German, Swiss and French farmers are now doing on-farm trials to see if the effects observed in the laboratory work on-farm in Europe. The farmers will also test interactions between using the fungi and a heather diet to optimise efficacy and hopefully validate this as a technique on-farm. Part of each flock will be managed using heather and/or fungi and part will be kept under standard management with weight gains, finishing times, faecal egg counts (FEC) and number of worm drenches all recorded.
Three farmers in Scotland – Katy Whitby-Last, Charlotte Blackler and Katherine Sharp (pictured below) – are involved in the trial and spoke during the workshop about their experiences and why they were involved with the project. All three are already using a range of techniques to reduce the need for anthelmintics in their livestock. This included planting diverse forages and trees, such as willows and oak, for animals to graze and browse and for collecting tree hay from willow, feeding sanfoin pellets, using planned grazing and retaining longer grass height in pastures.
Maintaining gut health came up as a key factor with cider vinegar and garlic mentioned – the aim was to make the gut as inhospitable as possible to parasites. One question from the Q&A session asked how much benefit is coming from bioactive forages and how much from the diverse forages rebalancing mineral and vitamin deficiencies and promoting overall animal and gut health. In other words, were all the techniques mentioned in this session fundamentally coming down to allowing natural immunity to develop by either a) providing a low level of larval infection and b) ensuring the immune system was functioning well due to minerals? The response from the researchers was that it was likely to be both.
In summary, even though we will have to wait for the results of the on-farm trial of the nematophagous fungi, it is clear there are a lot of things that farmers can incorporate into their farm management practices now to reduce the risk of worm infection. Introducing some different and diverse forages – and thinking about tree species that could be of benefit – and ensuring that all animals have the best nutrition and the right vitamin and mineral balance will help minimise the effect of worm infection – and improve other health issues, too.